The staff concluded that construction and operation of the projects would result in some adverse and significant environmental impacts but noted TransCanada could reduce those impacts to acceptable levels if it follows the company's and staff's recommendations.

The pipes are designed to move gas from the Marcellus and Utica shale producing regions in Pennsylvania, West Virginia and Ohio to consumers in the Southeast and Gulf Coast, including the liquefied natural gas export terminals under construction and in service along the Gulf of Mexico.

The 2.7 billion cubic feet per day Mountaineer project includes about 165 miles (266 kilometers) of new 36-inch (91.4 centimeter) pipe in West Virginia and three new compressor stations and upgrades to other compressors.

TransCanada said it expects the Mountaineer project to create about 9,000 jobs during construction in West Virginia.

The 0.875-bcfd Gulf project includes seven new compressor stations in Kentucky, Tennessee and Mississippi and upgrades to other compressors.

The projects together will cost about $2.7 billion, according to local media reports. TransCanada has said in the past it expects the projects to enter service in the fourth quarter of 2018.

FERC said the commissioners will take into consideration staff's recommendations when they make a decision on the projects. That decision, however, will have to wait until after agency has a quorum of commissioners that would enable it to make major decisions.